The present description generally relates to power system devices for monitoring, metering, protection and control of electric power systems, and more specifically, to a contact-input arrangement for power system devices.
In an electric power system, energy is generated and transported from the generating facilities to locations and loads requiring the energy. Electric power systems include a variety of power system equipment such as electrical generators, electrical motors, power transformers, power transmission lines, buses and capacitors, to name a few. The electric power systems also include power system devices such as monitoring devices, control devices, metering devices, and protective devices which monitor, control and protect power system equipment. High-speed communication is necessary among power system devices and between power system devices and power system equipment in order to provide reliable protection, metering, monitoring and control in an electric power system or grid.
FIG. 1 is a single line schematic diagram of an electric power system 10 that may be utilized in a typical wide area. As illustrated in FIG. 1, the power system 10 includes, among other things, three synchronous generators 11, 12 and 13, configured to generate three-phase sinusoidal waveforms such as 12 kV sinusoidal waveforms, three step-up power transformers 14a, 14b and 14c, configured to increase the generated waveforms to a higher voltage sinusoidal waveforms such as 138 kV sinusoidal waveforms and a number of circuit breakers 18. The step-up power transformers 14a, 14b, 14c operate to provide the higher voltage sinusoidal waveforms to a number of long distance transmission lines such as the transmission lines 20a, 20b, 20c and 20d. In an embodiment, a first substation 16 may be defined to include the two synchronous generators 11 and 12, the two step-up power transformers 14a and 14b and associated circuit breakers 18, all interconnected via a first bus 19. A second substation 35 may be defined to include the synchronous generator 13, the step-up power transformer 14c and associated circuit breakers 18, all interconnected via a second bus 25. At the end of the long distance transmission lines 20a, 20b, a third substation 22 may be defined to include bus 23, and two step-down power transformers 24a and 24b configured to transform the higher voltage sinusoidal waveforms to lower voltage sinusoidal waveforms (e.g., 15 kV) suitable for distribution via one or more distribution lines 26 to loads such as a load 32. The second substation 35 also includes two step-down power transformers 24c and 24d to transform the higher voltage sinusoidal waveforms, received via the second bus 25, to lower voltage sinusoidal waveforms suitable for use by respective loads 30 and 34.
A number of power system devices are connected at various points in the electric power system 10. For example, power system devices 100, 102 are shown operatively connected to select portions of the transmission line 20b. In general, a power system device such as 100, 102 may be configured to perform one or more of power system protection (e.g., a line current differential protection), automation (e.g., reclosing a circuit breaker), control (e.g., capacitor bank switching) and metering (e.g., power consumption calculation). Another power system device 104 may further monitor, control and/or automate power system devices 100, 102. For example, power system device 104 may be a programmable automation controller (PAC), which may be adapted to provide remote monitoring, data acquisition, control and automation of power system devices 100, 102. High-speed communication is necessary among power system devices 100, 102, 104 and between power system devices 100, 102, 104 and power system equipment in order to provide reliable protection, metering, monitoring and control in an electric power system or grid. For example, it is necessary for power system devices to quickly detect and isolate a fault on a transmission line.